As wireless communication technologies advance, various services using the position information of the portable terminal are growing. For example, the portable terminal can provide a service for searching desired establishments and attraction near the currently located area. Also, using the position information of the portable terminal, it is possible to locate a friend or a user himself/herself, or to efficiently arrange and manage workers and vehicles. Further, using the position information of the portable terminal, a service can be implemented to inform a guardian of a child of current position or a moving path of the child or an object.
The portable terminal typically estimates the position information using a Global Navigation Satellite System (GNSS) and a triangulation.
Using the GNSS, the portable terminal can estimate its position information by measuring a phase of a satellite signal sent from a GNSS satellite, or by estimating a code of the satellite code and measuring a distance to the satellite.
However, the portable terminal using the GNSS cannot receive the accurate satellite signal in a shadow zone of the satellite signal, for example, inside or near a building or in built-up areas, and thus cannot accurately estimate its position.